This invention relates to an extruded, open-cell microcellular alkenyl aromatic polymer foam and a process for making.
To significantly improve the performance of insulating systems, vacuum panel technology is currently being evaluated by industry. The absence of air or gas in the panels affords the possibility of substantial enhancement of insulating performance.
To further significantly improve the performance of insulating systems, microcellular foams (e.g., about 70 micrometers or less) are being evaluated by industry. The small cell size affords the possibility of substantial enhancement of insulating performance in many instances.
Extruded, closed-cell alkenyl aromatic polymer foams of medium cell size (e.g., 0.2 to 1.0 millimeter (mm)) have been employed in insulating systems for decades. They offer good insulating performance and excellent mechanical strength. However, the closed-cell structure makes them unsuitable for use in vacuum systems. Closed-cell foams cannot be evacuated of entrapped gas easily or without collapsing them.
A means to address the problem of inability to evacuate would be to employ an alkenyl aromatic polymer foam with very high open cell content. However, the only known microcellular, open-cell alkenyl aromatic polymer foams are those prepared by phase separation or with supercritical fluids as seen in U.S. Pat. Nos. 41,673,695; 4,473,665; 5,158,986; and 5,334,356. These foams are expensive to produce and have limited mechanical strength.
It would be desirable to have a strong, economical, microcellular, open-cell alkenyl aromatic polymer foam to employ in vacuum insulation systems. It would further be desirable to have such foams in a cell size range of about 70 micrometers or less.